Air Conditioner Troubleshooting

Easy step by step guide on how to troubleshoot your air conditioner, though appearances may vary the process is the similar. Problems are listed in order of popularity, this article pertains to most cars trucks and SUV's.

Difficulty Scale: 5 of 10

Tools and Supplies Needed

  • Air Conditioner Recharge Kit
  • Protective Eyewear
  • Work Gloves
Begin by parking your car on level ground with the emergency brake set, engine cool, wearing safety eye wear and gloves.

Step 1 - Using a test light check the A/C system fuses located in the PDC (power distribution center) replace any blown fuses and recheck. Please visit - Fuse Testing

Test Fuses
Step 2 - With the engine "ON" and the A/C turned to the coldest setting with the fan speed on high the compressor should be operating, on some models a clutch is used to engage the compressor which is easy to see. (Note: This can take up to 1 minute to come on after the engine is started.)

If the system is low on refrigerant it could cycle on and off, making a clicking noise. If the compressor clutch doesn't engage attach a pressure gauge or recharge kit to the low pressure side charge port to inspect system pressure readings. Please visit - AC System Recharge

Compressor Clutch Rotating
On some models an internal compressor valve is actuated which activates the pump, a gauge set is used to determine if the compressor is working. Please visit - AC System Pressure Test

Air Conditioner Gauge Set
Step 3 - If the level of refrigerant is low in the system it will not cool sufficiently. Please visit - AC System Recharge - Simple

A/C Recharge Kit
Step 4 - If the state of charge is sufficient and the compressor will still not engage, the electrical system must be checked. With the engine and AC system still "ON" carefully use a test light and check for power at the compressor or at the wiring harness near the compressor, if power is present and the compressor is not working replacement is needed. If no power is observed proceed to the next step.

Air Conditioner Compressor
Step 5 - Trigger power to the compressor is supplied by a relay or control unit, locate and test the relay, testing a climate controller itself is a little more difficult and requires a wiring diagram. Please visit - Relay Testing

Testing Air Conditioner Relay
Step 6 - The A/C system must be able to exchange the heat at the condenser or the system will not work, or work poorly, the most common cause for this condition is engine overheating which can be caused by a plastic bag lodged in the condenser or coolant leak.

It's also a good idea to use a garden hose to force water backwards through the radiator area, this will help remove road grime from the cooling fins of the condenser and radiator.

Coolant Leak
Step 7 - If a temperature blend door actuator is not functioning properly it will cause warm air from the heater to mix with cold air from the air conditioner. Start your car and allow the engine idle, turn the blower motor speed on the low speed setting, switch the temperature control from warm to cold while your ear is close to the center dash vent.

An audible noise should be heard as the door moves inside the heater box from open to closed position. If not, suspect a shorted servo actuator motor or a vacuum leak on older vehicles.

Blend Door Actuator
Step 8 - An electric blower motor forces air throughout the ventilation system, if this motor stops working no air will be exhausted from the vents.

Blower Motor
Step 9 - Most vehicles are equipped with a cabin air filter which can clog causing the air flow to be restricted.

Replacing Cabin Air Filter
If further assistance is needed, our certified technicians are ready to answer your car repair questions for free.

Best Practices

  • Service your A/C system about every three years, activate the system periodically to keep components lubricated.
Related Links

Article first published
Air Conditioner Recharge - Simple
Blend Door Actuator Replacement